Supercapacitors (also known as ultracapacitors or electrical double-layer capacitors) have the potential to replace Li ion batteries as the next-generation electrical energy storage technology in demanding applications due to their high power density and excellent cycling stability. Graphene-based supercapacitor electrodes are particularly promising because they feature high surface area, good electrical conductivity, and chemical inertness. Researchers at Lawrence Livermore National Laboratory have developed binder-free 3D mesoporous graphene macro-assemblies (GMAs) that have exceptionally high surface area (˜1500 m2/g) and excellent conductivity (˜100 S/m) using abundant and low cost starting materials. These GMAs offer many advantages over traditional carbon-based supercapacitor electrodes such as deterministic control over pore morphology, increased conductivity, and the absence of conductive filler and binder materials. However, the interfacial capacitance of graphene-based electrodes is limited by the low density of states at the Fermi level to ˜10 mF/cm2 (corresponding to 0.01 electron per carbon atom for the stability window of aqueous electrolytes). To replace Li-ion batteries in energy-demanding applications, these materials need improvements to their energy storage performance.
Fullerenes (also known as Bucky-balls) can store 10 times the energy per carbon as graphene (6 electrons per C60 molecule or 1 electron per 10 carbon atoms). Since the discovery of C60, fullerenes have attracted pronounced attention due to their applications in medicinal chemistry (as MRI contrast agents, in tumor diagnosis and radio-immunotherapy), material science and photovoltaic solar cells, among others. Functionalization or chemical modification of fullerenes has be used to increase their solubility, allow their characterization and explore their physical and chemical properties. Fullerenes possess highly reactive double bonds that allow the study of their reactivity using different types of reactions, such as oxidation reactions, transition metal complexation, hydrogenations, halogenations, radical additions, cycloadditions (1,3-dipolar, [2+2], [4+2], [3+2], [2+2+1]), addition of nucleophiles (Bingel additions), silylations and electrosynthesis.